In the electrophotography art, there is a need for relatively low fusing temperature toner powders having adequate offset latitude and good keeping performance. These toners are desirable because they permit a copier to operate at lower internal temperatures which increases the useful life of machine components in the copier such as the photoconductor films, electronic components, fuser roll and the like. These toners also reduce power consumption, copier warmup time, and problems with paper receivers and permit higher speed fusing.
To achieve such results, various approaches have been tried. One approach has been to utilize crosslinking monomers such as divinyl benzene in styrene/acrylic systems. However, this type of toner fuses at fairly high temperatures, nearly 400.degree. F., which can adversely affect the fusing subsystem and adjacent components in the copier.
Blends of high molecular weight polymers have been shown to provide good offset latitude for low fusing temperatures. However, these materials are difficult to manufacture because the polymers have very different viscosities and do not melt-blend easily.
U.S. Pat. No. 4,217,406 discloses toners that use polymers that are crosslinked during meltkneading. Unfortunately, many of these polymers cannot be practically manufactured because the kinetics of the crosslinking reaction are too slow. If the reaction is too rapid, the material can degrade if processing continues for too long of a time period.
So far as is now known, the prior art approaches have not solved the problem of providing a toner powder with low fusing temperatures and adequate offset latitude.